Presented at the Global Azure Bootcamp 2019, Melbourne, Australia.

1. Paco de la Cruz
Durable Functions
Serverless and Stateful Orchestrations on Azure
@pacodelacruz
Global Azure Bootcamp 2019, Melbourne

2. @pacodelacruz
linkedin.com/in/pacodelacruz
pacodelacruzag.wordpress.com
slideshare.net/pacodelac/presentations

3. Agenda
Durable

4. Cloud compute spectrum

5. Azure compute spectrum

6. Azure compute spectrum

7. “Serverless” and its benefits
Event-driven scaling
not resource-driven
Pay only for what
you use
Server abstraction
Focus on value

8. Azure Functions in a nutshell
Event Triggers Code Outputs
React and get inputs from
a growing list of services
(triggers and input
bindings)
C#, F#,
Node.js, Java,
Python (Preview)
Send results to a
growing list of services
(output bindings)

9. Some limitations/challenges of Azure Functions
Manageable Sequencing
+ Error Handling / Compensation

10. Manageable Sequencing
+ Error Handling / Compensation
Some limitations/challenges of Azure Functions
Fanning-out & Fanning-in

11. Some limitations/challenges of Azure Functions
Manageable Sequencing
+ Error Handling / Compensation
Fanning-out & Fanning-in
Async Long-Running Http APIs
(Status polling)
Start
Get Status

12. Some limitations/challenges of Azure Functions
Manageable Sequencing
+ Error Handling / Compensation
Fanning-out & Fanning-in Async Long-Running Http APIs
(Status polling)
Start
Get Status
Long-Running Stateful
Repeating Process

13. Some limitations/challenges of Azure Functions
Manageable Sequencing
+ Error Handling / Compensation
Fanning-out & Fanning-in
Long-Running Stateful
Repeating Process
Async Long-Running Http APIs
(Status polling)
Start
Get Status
Human Interaction

14. Some limitations/challenges of Azure Functions
Manageable Sequencing
+ Error Handling / Compensation
Fanning-out & Fanning-in
Human InteractionLong-Running Stateful
Repeating Process
Async Long-Running Http APIs
(Status polling)
Start
Get Status
External Events Correlation

15. Some limitations/challenges of Azure Functions
Manageable Sequencing
+ Error Handling / Compensation
Fanning-out & Fanning-in
Human InteractionLong-Running Stateful
Repeating Process
Async Long-Running Http APIs
(Status polling)
Start
Get Status
External Events Correlation

16. Durable Function Patterns
Function Chaining Fanning-out & Fanning-in Async HTTP APIs
Human InteractionMonitoring External Events Correlation
Start
Get Status

17. Durable Functions in a nutshell
Based on
Durable Task Framework
Persistence on Azure Storage
(Fully Managed and Abstracted)
To Implement stateful
workflows-as-code
(C#, F#, Java and Node.js)
Azure Functions
Extension

18. Durable Functions Components
Activity Function Activity Function Activity Function
Orchestrator Function
Orchestration Client

19. Durable Functions Components
Activity Function Activity Function Activity Function
Orchestrator Function
Orchestration Client
Stateful
Process Manager
Call Activity Functions
Advanced Retries
Error Handling
Fall Back / Compensation
Checkpointing
Dehydrates during activities
Rehydrates at responses / events

20. Durable Functions Components
Activity Function Activity Function Activity Function
Orchestrator Function
Orchestration Client
Stateless
Single Step
Inputs and Outputs
Stateful
Process Manager
Call Activity Functions
Advanced Retries
Error Handling
Fall Back / Compensation
Checkpointing
Dehydrates during activities
Rehydrates at responses / events

21. Durable Functions Components
Activity Function Activity Function Activity Function
Orchestrator Function
Orchestration Client
Start
Get Status
Send Event
Wait for Completion
Terminate
Stateless
Single Step
Inputs and Outputs
Stateful
Process Manager
Call Activity Functions
Advanced Retries
Error Handling
Fall Back / Compensation
Checkpointing
Dehydrates during activities
Rehydrates at responses / events

22. Orchestration Function Limitations
Orchestration code must
• Be deterministic
(e.g. no NewGuid(), Random, DateTime.Now(), Http calls, etc.)
• Be non-blocking: (no I/O, Thread.Sleep(), etc.)
• Never initiate any async operations: without using its
context
• Avoid infinite loops
There are workarounds

23. Orchestration Considerations
Activity function calls and responses are sent via queues
Async calls persist the orchestration state into a storage table
Activity function outputs are persisted (Event Sourcing)
Activity function responses, timer or external events will recover
the persisted orchestration state into memory
The orchestration is replayed up-to the last persisted point
Activity Functions are not replayed

24. Function Chaining Pattern
public static async Task<object> Run(
[OrchestrationTrigger] DurableOrchestrationContext ctx)
{
try
{
var x = await ctx.CallActivityAsync<object>("F1");
var y = await ctx.CallActivityAsync<object>("F2", x);
return await ctx.CallActivityAsync<object>("F3", y);
}
catch (Exception ex)
{
// error handling / fall back / compensation
}
}

25. Function Chaining Pattern
public static async Task<object> Run(
[OrchestrationTrigger] DurableOrchestrationContext ctx)
{
try
{
var x = await ctx.CallActivityAsync<object>("F1");
var y = await ctx.CallActivityAsync<object>("F2", x);
return await ctx.CallActivityAsync<object>("F3", y);
}
catch (Exception ex)
{
// error handling / fall back / compensation
}
}

26. Function Chaining Pattern
public static async Task<object> Run(
[OrchestrationTrigger] DurableOrchestrationContext ctx)
{
try
{
var x = await ctx.CallActivityAsync<object>("F1");
var y = await ctx.CallActivityAsync<object>("F2", x);
return await ctx.CallActivityAsync<object>("F3", y);
}
catch (Exception ex)
{
// error handling / fall back / compensation
}
}

27. Fan-out & Fan-In Pattern
public static async Task<int> Run(
[OrchestrationTrigger] DurableOrchestrationContext ctx)
{
object[] workBatch = await ctx.CallActivityAsync<object[]>("F1");
var tasks = new Task<long>[workBatch.Length];
for (int i = 0; i < workBatch.Length; i++)
{
tasks[i] = ctx.CallActivityAsync<int>("F2", workBatch[i]);
}
await Task.WhenAll(tasks);
long sum = tasks.Sum(t => t.Result);
return sum;
}

28. Fan-out & Fan-In Pattern
public static async Task<int> Run(
[OrchestrationTrigger] DurableOrchestrationContext ctx)
{
object[] workBatch = await ctx.CallActivityAsync<object[]>("F1");
var tasks = new Task<long>[workBatch.Length];
for (int i = 0; i < workBatch.Length; i++)
{
tasks[i] = ctx.CallActivityAsync<int>("F2", workBatch[i]);
}
await Task.WhenAll(tasks);
long sum = tasks.Sum(t => t.Result);
return sum;
}
CallActivityWithRetryAsync

29. Orchestration Client
public static async Task<HttpResponseMessage> Run(
[HttpTrigger(AuthorizationLevel.Function, methods: "post",
Route = "orchestrators/{functionName}")] HttpRequestMessage req,
[OrchestrationClient] DurableOrchestrationClientBase starter, ILogger log)
{
// Function input comes from the request content.
dynamic eventData = await req.Content.ReadAsAsync<object>();
string instanceId = await starter.StartNewAsync("myOrchestrator", eventData);
log.LogInformation($"Started orchestration with ID = '{instanceId}'.");
var res = starter.CreateCheckStatusResponse(req, instanceId);
return res;
}

30. Orchestration Client
public static async Task<HttpResponseMessage> Run(
[HttpTrigger(AuthorizationLevel.Function, methods: "post",
Route = "orchestrators/{functionName}")] HttpRequestMessage req,
[OrchestrationClient] DurableOrchestrationClientBase starter, ILogger log)
{
// Function input comes from the request content.
dynamic eventData = await req.Content.ReadAsAsync<object>();
string instanceId = await starter.StartNewAsync("myOrchestrator", eventData);
log.LogInformation($"Started orchestration with ID = '{instanceId}'.");
var res = starter.CreateCheckStatusResponse(req, instanceId);
return res;
}

31. Orchestration Client
public static async Task<HttpResponseMessage> Run(
[HttpTrigger(AuthorizationLevel.Function, methods: "post",
Route = "orchestrators/{functionName}")] HttpRequestMessage req,
[OrchestrationClient] DurableOrchestrationClientBase starter, ILogger log)
{
// Function input comes from the request content.
dynamic eventData = await req.Content.ReadAsAsync<object>();
string instanceId = await starter.StartNewAsync("myOrchestrator", eventData);
log.LogInformation($"Started orchestration with ID = '{instanceId}'.");
var res = starter.CreateCheckStatusResponse(req, instanceId);
return res;
}

32. Durable Functions vs Logic Apps?
vs
Durable Functions Logic Apps
Both allow implementing advanced workflow patterns
C#, F#, Java, JavaScript Visual designer and WDL
Bindings (~ 20 supported) 250+ connectors
Portable Runtime Runs only on Azure
Monitoring based on App Insights & APIs Rich monitoring & management tools
Serverless + dedicated & isolated Serverless + dedicated & isolated (ISE)
platform.deloitte.com.au/articles/azure-durable-functions-vs-logic-apps

33. Additional Resources
Twitter @azurefunctions
Documentation aka.ms/durablefunctions
Live Web Cast aka.ms/azurefunctionslive
Repos github.com/Azure/azure-functions-durable-extension
github.com/Azure/azure-functions-durable-js
Samples github.com/Azure/azure-functions-durable-
extension/tree/master/samples
Pluralsight course app.pluralsight.com/library/courses/
azure-durable-functions-fundamentals

34. Any questions so far?

35. Let’s have
some fun!

36. Demo 1
Development and Debugging
Furry Models
Cat Application Approval via email

37. Orchestration
Function
Start
Send Approval
Request via Email
Create Timer
External
Event
Timer
Expires
WhenAny
Move Blob to
Corresponding Container
End
(Requests
blob container)
(Approved or Rejected
blob container)

38. Orchestration
Function
Start
Send Approval
Request via Email
Create Timer
External
Event
Timer
Expires
WhenAny
Move Blob to
Corresponding Container
End
BlobTrigger
Function
HttpTrigger
Process Approval
(Requests
blob container)
(Approved or Rejected
blob container)
Orchestration Client Activity Functions
ActivityTrigger
Send Approval
Request via Email
ActivityTrigger
Move Blob to
Corresponding Container
HttpTrigger
Check Status

39. Demo 2
Execution & Monitoring on Azure
Furry Models
Cat Application Approval via Slack

40. Orchestration
Function
Start
Send Approval
Request via Slack
Create Timer
External
Event
Timer
Expires
WhenAny
Move Blob to
Corresponding Container
End
BlobTrigger
Function
HttpTrigger
Process Approval
(Requests
blob container)
(Approved or Rejected
blob container)
Orchestration Client Activity Functions
ActivityTrigger
Send Approval
Request via Slack
ActivityTrigger
Move Blob to
Corresponding Container
HttpTrigger
Check Status

41. Let your Cat apply!
Great opportunity to get famous!
Send to: …@...com
Subject: I want to be a Furry Model!
Attach your cat best picture

42. Details about the demos:
platform.deloitte.com.au/articles/azure-durable-functions-approval-workflow-with-sendgrid
platform.deloitte.com.au/articles/azure-durable-functions-approval-workflow-with-slack
github.com/pacodelacruz/durable-functions-furry-models

43. Q & A

44. Thanks!

45. @pacodelacruz
linkedin.com/in/pacodelacruz
pacodelacruzag.wordpress.com
slideshare.net/pacodelac/presentations